P1258critical severityPowertrain

Engine Coolant Overtemperature Protection Mode Active

on 2010 GMC Terrain 2.4L I4 · FWD

What this code means

The PCM has activated engine protection mode due to excessive coolant temperature. The PCM may reduce power output, disable cylinders, or limit RPM to prevent engine damage from overheating. This is a serious code that requires immediate attention.

Symptoms

Reduced Engine Power message
Engine overheating
Temperature gauge in red zone
Loss of power
Engine may shut down
A/C system disabled

Common causes

Low coolant level
Failed water pump
Stuck closed thermostat
Blocked radiator
Faulty coolant temperature sensor
Head gasket failure
Cooling fan failure
Collapsed radiator hose

Diagnostic steps

Check coolant level immediately
Inspect for coolant leaks
Test thermostat operation
Check water pump for flow
Test cooling fans
Inspect radiator for blockage
Pressure test cooling system
Check head gasket (combustion gas test)

Repair notes

Do not continue driving. Check coolant level and look for leaks immediately. Continued overheating will cause severe engine damage including head gasket failure and warped heads.

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